1. Field of the Invention
This invention relates to easy-open metallic containers, which are defined as being openable by a consumer without a can opener or other tool, and methods for making such containers. More specifically, this invention relates to an improved method for making a full open type easy-open closure that provides consumers protection against finger cuts while at the same time being resistant to pressure-induced failure.
2. Description of the Related Technology
An easy open end, for the purposes of this document, may be defined as a can end that is designed to be opened by a consumer without using a can opener or similar tool. A full-open type can end is, as opposed to a pour-type easy-open can end, designed to be completely removable from the can end during opening to provide unimpeded access to the inside of the can. Full-open type can ends are commonly utilized for packaging loose solids, such as mixed nuts or coffee, while pour-type can ends tend to be utilized for soft drinks or other beverages. Full-open type easy-open can ends are also used for packaging products of a non-food nature, such as tennis balls, which must be kept in a pressurized environment after manufacture to avoid deformation, particularly in the seam area.
When an end panel of an easy-open type closure separates as designed at a score line during opening, the resulting edges tend to be sharp, posing a possible danger to the consumer. One solution to this problem was presented in U.S. Pat. 3,705,363 to Elser. FIGS. 1 and 2 depict a can end and method of making as it is described in the Elser patent. As may be seen in FIG. 1, the Elser patent describes a container 10 having a full open closure 12 that includes a panel 13 and a circumferential score 14. A gripping tab 16 is riveted to the end panel 13 for the purpose of rupturing the score 14 when the gripping tab 16 is lifted by a consumer. Referring to FIG. 2, the closure 12 further includes a safety fold 17 that is formed by the interaction of die members 18, 20, 22 and 24. As may be seen in FIG. 2, safety fold 17 includes a lower bead 28 that is radiused so as to be unitary with the end panel 13 at one end and further unitary at a second end with an intermediate panel 30 that overlies panel 13 at a second, opposite end. Safety fold 17 further includes an upper bead 26 that is radiused so as to be unitary with the intermediate panel 30 at one end thereof and similarly with an upper panel 32 at a second end thereof that overlies the intermediate panel 30. A transition portion 34 is unitary with the upper panel 30 at one end and transitions the upper panel 32 into the blank 36 that is used to form the double seam connecting the closure 12 to the sidewall of the container 10.
As can be visualized by viewing FIG. 2, the upper bead 26, because it protrudes slightly inwardly of the leftward edge of score 14, will be positioned to contact a consumer""s finger before the consumer""s finger contacts with the potentially sharp edge that is formed during separation of the end panel 13 at the score line 14 during opening. As a result, some protection is afforded by this design to the consumer against finger cuts.
In the embodiment of the Elser patent that is depicted in FIG. 2, the intermediate panel 30 and the upper panel 32 are positioned so as to be roughly parallel to reach other, and also roughly parallel to the underlying end panel 13. In practice, however, it has been common to manufacture such closures as is instead shown in FIG. 3. In this configuration, the intermediate panel 30xe2x80x2 is inclined with respect to the end panel 13 so as to form an angle A1 opening radially inwardly. This angle A1 and a second angle A2 that is defined between the upper panel 32xe2x80x2 and the end panel 13 and that also opens radially inwardly toward the center of the end panel 13, are both designed to be about five or six degrees.
Unfortunately, the configurations that are shown in FIGS. 2 and 3 have been found to be susceptible to pressure induced failure, which occurs when the container 10 is given a positive pressure, such as is required in the packaging of tennis balls. The present inventor has studied the mechanism by which this occurs, and has determined that the interior pressure causes the end panel 13 of the closure 12 to bow upwardly, with the greatest deformation occurring in the centermost part of the panel 13. As this occurs, the outward portions of the end panel 13 are pulled radially inwardly, or to the right as it is viewed in FIG. 3. This causes the lower bead 28 to begin to open, meaning that the angle A1 begins to increase, which reduces the overall strength of the safety fold 38. This culminates in a failure of the closure 12 that is symptomized by an outward folding of the closure 12 over the safety fold 38, the fold line tending to be oriented generally radially.
A need exists for an improved process for manufacturing a safety easy opening end that is more resistant to pressure induced failure than conventional closures of this type, such as those that are discussed above with reference to FIGS. 1-3.
Accordingly, it is an object of the invention to provide an improved process for manufacturing a safety easy opening end that is more resistant to pressure induced failure than conventional closures of this type.
In order to achieve the above and other objects of the invention, a method of making a safety easy-open end for a container includes, according to a first aspect of the invention, steps of providing an end blank having an end panel that extends substantially within a first plane and a circumferential outer double-seaming portion; scoring the end panel to define a removable area; forming the end blank to define a safety fold including an intermediate panel that is unitary with and overlies the end panel and that is connected to the end panel by a first bead, a top panel that extends substantially within a second plane and is unitary with and overlies the intermediate panel and that is connected to the intermediate panel by a second, safety bead, and a transition region that is unitary with and connects the top panel to the double-seaming portion; and wherein step (c) is performed so that said first and second planes intersect at said end panel at a location that is radially inward from said first bead; and securing an opening tab to the end panel. According to a second aspect of the invention, a method of making a safety easy-open end for a container includes steps of providing an end blank having an end panel that extends substantially within a first plane and a circumferential outer double-seaming portion; scoring the end panel to define a removable area; forming the end blank to define a safety fold including an intermediate panel that extends substantially within a third plane and is unitary with and overlies the end panel and that is connected to the end panel by a first bead, a top panel that extends substantially within a second plane and is unitary with and overlies the intermediate panel and that is connected to the intermediate panel by a second, safety bead, and a transition region that is unitary with and connects the top panel to the double-seaming portion; and wherein step (c) is performed so that said first and third planes intersect at said end panel at a location that is radially inward from said first bead; and securing an opening tab to the end panel.
These and various other advantages and features of novelty that characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.